Linebarrels of Iron (鉄のラインバレル, Kurogane no Rainbareru) is a Japanese manga series created by Eiichi Shimizu and Tomohiro Shimoguchi. The series was first serialized in Akita Shoten's monthly shōnen manga magazine, Champion Red, in 2005. It has since been compiled into 24 tankōbon, as of October 20, 2014.

An anime adaptation of the manga series was announced in the February issue of Animage magazine. The anime is directed by Masamitsu Hidaka and animated by Gonzo. Though the world premiere of the first episode took place at Southern California's 2008 Anime Expo, the series premiered in Japan on the television network TBS (Tokyo Broadcasting System) on October 3, 2008. The anime broadcast a total of twenty-four episodes, the last of which aired on March 20, 2009. To commemorate the series' anime adaptation, Shimizu and Shimoguchi decided to create a one shot manga, recreating the entire first episode of the anime, in which the plot differs in many aspects compared to the beginning of the manga.

Fourteen-year-old Kouichi Hayase’s life has always been a mediocre one, if not dismal. However, those days of being bullied by classmates and escaping to a fantasy of being a hero are put to an end when a certain “accident” bestows on him a girl and a gigantic humanoid robot called “LINEBARREL”. The extraordinary power that Kouichi obtains puts him and everything around him on a sudden rollercoaster ride of battles, intrigues and friendship! During the course of his adventure, the boy starts to learn what life has to offer; he meets new friends, bids farewell to the old ones, but most of all he now has considerable responsibilities and is forced to confront the world around him.